For a really kicking atmosphere, the only Christmas do to be at this year is the one at the Large Hadron Collider beneath the Franco-Swiss border.

It's had a bumper few months and everybody wants a piece of it – which is why the team is ready to party! They're all there in their Santa hats and flashing reindeer antlers and if you ask them, they'll tell you the mathematical formula for calculating the speed at which each antler flashes – see, who says physicists don't have small talk?

The tree is up, with its baubles clustered to represent the structure of atoms – red electrons around a silver nucleus – and at the top is a photo of Einstein, the famous one with his tongue out, on which someone has scrawled "Enjoyment equals Merry Christmas Squared", the so-called Happiness Equation whose abbreviation is known around the world.

A steaming barrel in the corner is marked Atomic Fusion and great ladles of the punch are being poured for the impromptu choir that has formed. Thus fortified they break into song. "O come all ye protons", "While shepherds watched their quarks by night", "I'm dreaming of a binomially expanded universe, just like the ones we used to know."

They're an eccentric bunch, with unusual skills. One of them has built a nativity scene in the shape of a boat, a bit like Noah's Ark. He's called it HMS Cern, and it's skippered by – who else? – a papier-mâché Captain Higgs. "So who's the fella at the back?" asks someone, pointing to a salty sea-dog type, made out of a wooden clothes peg and complete with tiny pipe and tobacco-stained cotton-wool beard (the alert among you may see where this is going). "Him? Why, that's Higgs' bo'sun of course!"

The LHC itself is bedecked with lights and decorations. Someone has left the door open and a piece of tinsel falls inside and is whizzed back to Christmas 1973 where it appears in a living room in Dumfries. A minute later one of the older scientists in the team recognises something on the floor. It's an old-style Christmas tree light, the filament visible through the cracks in the paint. His family had ones like this. Suddenly, his vision blurs and he's seven again, standing outside the living-room door, seeing the glow. And the truth of those long ago Christmastimes pierces him: how it was always the before that was the sweetest moment.